According to the state of the art, pressure loadable transmission means applicable for curved transmission paths as well as for straight transmission paths consist, e.g., of a series of transmission members guided in a suitable guide channel, the members being spherical or dumbbell-shaped. For a line of dumbbell-shaped members to be curveable in all directions, the contact faces of the members are convex as is the case with spherical members. This means that in both cases the transmission members are in contact with each other in a very small area (theoretically at one point) whether they are arranged in a straight line or in a curved line. The whole force is transmitted through this contact point. Therefore, a line of such transmission members, even a straight line, is very unstable and tends to buckle. Because of buckling, the members exert radial forces on the guide means, even on a straight transmission path, resulting in a considerable loss of force through friction and requiring a strong design of the guide means.
In the publication U.S. Pat. No. 3,518,051, a force transmission means of this general type having spheres as force transmission members is described. Publication U.S. Pat. No. 3,968,861 describes a force transmission means of a similar type with dumbbell-shaped transmission members. These members have convex contact faces and, for reducing friction, comprise rollers rolling on rolling surfaces of the guide means.
The publications CH-646762 (or U.S. Pat. No. 4,397,145) and CH-656683 describe force transmission means in the form of chains which are pressure or tension loadable and which comprise mutually connected transmission members of a substantially spherical form. Such chains also buckle easily in straight-line pushed operation and, therefore, must be guided correspondingly.